Silurian and earliest Devonian birkeniid anaspids from the Northern Hemisphere

Blom, Henning; Märss, Tiiu; Miller, C. Giles

doi:10.1017/s0263593300000250

Cited by 47 publications

(89 citation statements)

References 29 publications

(54 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, there are a number of remains with osteostracan and anaspid affinities that are too worn or too fragmentary to be identified. The majority of the vertebrates found in this study have already been described from Gothemshammar or figured in open nomenclature (Martinsson, 1966;Gross, 1968;Fredholm, 1990;Blom et al, 2002;Märss et al, 2014), and our descriptions focus on the new scale types and sculpture patterns belonging to taxa not reported from Gothemshammar before.…”

Section: Vertebratesmentioning

confidence: 92%

“…These specimens were to some extent revised by Blom et al (2002), which will be further commented on below. The samples treated here contain scales from several anaspid species, all of which have been reported from Gotland before (Fredholm, 1990;Blom et al, 2002) and belong to the order Birkeniida Berg, 1937. There are also a number of other fragments, such as spines (Fig.…”

Section: Anaspidsmentioning

confidence: 99%

“…Märss, 1989;Turner, 1999). However, towards the Wenlock/Ludlow boundary diverse faunas containing many thelodont, osteostracan, and anaspid taxa have been found in several areas of the Baltic Basin (Fredholm, 1990;Blom et al, 2002;Märss et al, 2007Märss et al, , 2014. This diversity peak is more or less contemporaneous in both the Eastern Baltic region and Gotland (Sweden), but equally diverse faunas have been reported from younger sediments of the East Baltic (Blom et al, 2002;Märss et al, 2007Märss et al, , 2014.…”

Section: Introductionmentioning

confidence: 99%

“…However, towards the Wenlock/Ludlow boundary diverse faunas containing many thelodont, osteostracan, and anaspid taxa have been found in several areas of the Baltic Basin (Fredholm, 1990;Blom et al, 2002;Märss et al, 2007Märss et al, , 2014. This diversity peak is more or less contemporaneous in both the Eastern Baltic region and Gotland (Sweden), but equally diverse faunas have been reported from younger sediments of the East Baltic (Blom et al, 2002;Märss et al, 2007Märss et al, , 2014. Thelodonts seem to have spread across a wide range of environments (Märss et al, 2007), but facies associations of anaspids and osteostracans indicate that these groups preferred lagoon and shoal areas (Märss and Einasto, 1978;Sansom, 2008;Märss et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

End-Wenlock terminal Mulde carbon isotope excursion in Gotland, Sweden: Integration of stratigraphy and taphonomy for correlations across restricted facies and specialized faunas

Jarochowska

Bremer

Heidlas

et al. 2016

Palaeogeography, Palaeoclimatology, Palaeoecology

View full text Add to dashboard Cite

Section: Vertebratesmentioning

confidence: 92%

Section: Anaspidsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

End-Wenlock terminal Mulde carbon isotope excursion in Gotland, Sweden: Integration of stratigraphy and taphonomy for correlations across restricted facies and specialized faunas

Jarochowska

Bremer

Heidlas

et al. 2016

Palaeogeography, Palaeoclimatology, Palaeoecology

View full text Add to dashboard Cite

“…Perhaps closer comparison may be drawn with the isopedin layer (L3) of the pteraspidomorph dermal skeleton. However, unlike isopedin, the anaspid lamellar tissue is often extensively vascularised (Gross, 1958;Blom et al, 2001;Donoghue and Sansom, 2002;Donoghue et al, 2006). Anaspids scales are almost always ornamented with tubercles, yet it is uncertain whether these correspond to odontodes.…”

Section: The Pleisiomorphic Condition Of the Vertebrate Dermal Skeletonmentioning

confidence: 99%

Histology of the heterostracan dermal skeleton: Insight into the origin of the vertebrate mineralised skeleton

Keating

Marquart

Donoghue

2015

Journal of Morphology

View full text Add to dashboard Cite

Living vertebrates are divided into those that possess a fully formed and fully mineralised skeleton (gnathostomes) versus those that possess only unmineralised cartilaginous rudiments (cyclostomes). As such, extinct phylogenetic intermediates of these living lineages afford unique insights into the evolutionary assembly of the vertebrate mineralised skeleton and its canonical tissue types. Extinct jawless and jawed fishes assigned to the gnathostome stem evidence the piecemeal assembly of skeletal systems, revealing that the dermal skeleton is the earliest manifestation of a homologous mineralised skeleton. Yet the nature of the primitive dermal skeleton, itself, is poorly understood. This is principally because previous histological studies of early vertebrates lacked a phylogenetic framework required to derive evolutionary hypotheses. Nowhere is this more apparent than within Heterostraci, a diverse clade of primitive jawless vertebrates. To this end, we surveyed the dermal skeletal histology of heterostracans, inferred the plesiomorphic heterostracan skeleton and, through histological comparison to other skeletonising vertebrate clades, deduced the ancestral nature of the vertebrate dermal skeleton. Heterostracans primitively possess a fourlayered skeleton, comprising a superficial layer of odontodes composed of dentine and enameloid; a compact layer of acellular parallel-fibred bone containing a network of vascular canals that supply the pulp canals (L1); a trabecular layer consisting of intersecting radial walls composed of acellular parallel-fibred bone, showing osteon-like development (L2); and a basal layer of isopedin (L3). A three layered skeleton, equivalent to the superficial layer L2 and L3 and composed of enameloid, dentine and acellular bone, is possessed by the ancestor of heterostracans 1 jawed vertebrates. We conclude that an osteogenic component is plesiomorphic with respect to the vertebrate dermal skeleton. Consequently, we interpret the dermal skeleton of denticles in chondrichthyans and jawless thelodonts as independently and secondarily simplified. J.

show abstract

TheEvolution of theZygomaticBoneFromAgnatha toTetrapoda

Gai

Zhu

2016

The Anatomical Record

View full text Add to dashboard Cite

Establishing the homology of the zygomatic or jugal bone and tracing its origin and early evolution represents a complex issue because of large morphological gaps between various groups of vertebrates. Using recent paleontological findings, we discuss the deep homology of the zygomatic or jugal bone in stem gnathostomes (placoderms) and examine its homology and modifications in crown gnathostomes (acanthodians, chondrichthyans and osteichthyans). The discovery of the placoderm Entelognathus from the Silurian of China ( 423 million years ago) established that the large dermal plates in placoderms and osteichthyans are homologous. In Entelognathus, the jugal was joined by a new set of bones (premaxilla, maxilla, and lachrymal), marking the first appearance of the typical vertebrate face found in tetrapods including humans. In non-Entelognathus placoderms, the jugal (homologized with the suborbital plate) occupied most of the cheek region and covered the palatoquadrate laterally. In antiarch placoderms (the most basal jawed vertebrates), the jugal (represented by the ventrally positioned mental plate) functioned as part of the upper jaw. In osteichthyans, the preopercular arose as a novel bone and separated the jugal from the opercular in piscine osteichthyans. A single bone in basal osteichthyans, the preopercular may have divided into two or three elements (the preopercular, the squamosal and/or the quadratojugal) in several later osteichthyan groups. Subsequent modifications of the jugal in the fish-tetrapod transition (its enlargement leading to its contact with the quadratojugal and the separation of the squamosal from the maxilla) brought the vertebrate face to the typical model we see in living tetrapods.

show abstract

Silurian and earliest Devonian birkeniid anaspids from the Northern Hemisphere

Cited by 47 publications

References 29 publications

End-Wenlock terminal Mulde carbon isotope excursion in Gotland, Sweden: Integration of stratigraphy and taphonomy for correlations across restricted facies and specialized faunas

End-Wenlock terminal Mulde carbon isotope excursion in Gotland, Sweden: Integration of stratigraphy and taphonomy for correlations across restricted facies and specialized faunas

Histology of the heterostracan dermal skeleton: Insight into the origin of the vertebrate mineralised skeleton

TheEvolution of theZygomaticBoneFromAgnatha toTetrapoda

Contact Info

Product

Resources

About